1. Field of the Invention
This invention relates to novel laked azo pigments, processes for their preparation and to paint, plastic and ink compositions containing such pigments.
2. Description of Related Art
Metal salts of individual azo compounds containing a pyrazolone moiety containing two sulfo groups are known in the art as pigments.
For example, German Patent 2,616,981 describes metal salts of pyrazolone azo dyes which are obtained by coupling diazotized 2-amino-4, 5-dichlorobenzene-1-sulfonic acid with 1-(sulfoaryl)-3-methyl-5-pyrazolone compounds and subsequent laking with metal salts.
Japanese Patent 62,166,359 describes electrophotographic toners that contain monoazo pigments of the formula ##STR2## X=Cl or SO.sub.3.sup.- ; m=1 or 2; M=Mg, Ca or Ba; n=1 or 2 When X is Cl, then m is 1 and n is 2, and when X is SO.sub.3.sup.-, then m is 2 and n is 1,
U.S. Pat. No. 4,594,411 describes ##STR3## wherein R is CH.sub.3 or COO.sup.- ; X is Cl, CH.sub.3,CH.sub.3 O, C.sub.2 H.sub.5 O C.sub.2 H.sub.5 CONH, NH.sub.2 CONH, C.sub.6 H.sub.5 CONH, CH.sub.3 SO.sub.2 NH, CH.sub.3 CONH, or hydrogen; Y is hydrogen, Cl, or CH.sub.3 ; Z is hydrogen or Cl, n is 0, 1 or 2; Me.sup.+ is one equivalent of a cation selected from the group consisting of NH.sub.4.sup.+, Li.sup.+, K.sup.+, Na.sup.+, 1/2 Sr.sup.2+, 1/2 Mn.sup.2+, 1/2 Ni.sup.2+, 1/2 Ba.sup.2+, 1/2 Mg.sup.2+ and 1/2 Ca.sup.2+ ; with the provision that if R is COO.sup.-, the additional equivalent charge is compensated by a further equivalent of said or another cation.
European Patent 0,126,405(German Patent 33,180,373) also describes laked pyrazolone azo pigments of the formula ##STR4## wherein D is tri or tetrasubstituted phenyl ring; R is CH.sub.3 or COO.sup.- ; X is Cl, Br, CH.sub.3, CH.sub.3 O, C.sub.2 H.sub.5 O CH.sub.3 CONH, SO.sub.2 NH.sub.2, SO.sub.3.sup.- ; Y is Cl, Br, CH.sub.3 or SO.sub.3.sup.- ; Z is Cl, Br or CH.sub.3.
U.S. Pat. No. 5,047,517 relates to a yellow monoazo pigment which is obtained by diazotization of 2-amino-4-chloro-5-methylbenzene-1-sulfonic acid, coupling of the diazonium compound with 1-(3'-sulfophenyl)-3-methyl-5-pyrazolone and subsequent laking of the coupling product to the calcium salt.
International Application WO 96/22334 describes an azo pyrazolone compound of formula ##STR5## in the form of a salt and its use as a pigment.
There is a desire, however, to obtain pigments having redder shades of yellow with high heat stability and ease of preparation as well as reduced cost. There is a need for these yellow pigments to show improved performance in one or more of the following properties: color strength, resistance to polar solvents and lightfastness.